Conventionally, a working vehicle such as an excavating working machine is known in which a working hydraulic actuator is driven by hydraulic oil sent from a fixed displacement type hydraulic pump. For example, the Patent Literature 1 describes an excavating working machine in which a first hydraulic pump, a second hydraulic pump, a third hydraulic pump and a fourth hydraulic pump are provided in series on an output shaft of an engine. According to the excavating working machine, the third hydraulic pump is a fixed displacement type hydraulic pump, and hydraulic oil is sent from the fixed displacement type hydraulic pump to working hydraulic actuators such as a turning motor, an arm cylinder, an offset cylinder, a boom cylinder and a bucket cylinder so as to drive them.